This invention relates to a snow-sweeping roller, such as a bristle-equipped sweeping roller, for replaceable attachment to a utility road vehicle. The roller is rotatably hung on the vehicle about a horizontal longitudinal axis, which can be set at a slant with respect to the longitudinal axis of the vehicle. The roller rotation can be counter to the wheels of the forwardly moving vehicle.
Snow-sweeping rollers are well known. They are used for the so-called "black clearance" of snowy streets in which snow is removed to the surface of any underlying asphalt. Tests have shown that the combined use of a roller with a snow plow and/or salt spreading device is especially advantageous. In particular, rollers make it possible to reduce considerably the amount of salt that is spread. The use of a snow-sweeping roller, however, is suitable only for snow depths up to a few centimeters, and then in tandem with another snow clearing unit. The snow-sweeping roller ejects snow laterally, according to its slant position relative to the main vehicle under the condition that the roller has a certain, minimum rotational speed. Such a snow-sweeping roller can be affixed to the front or rear side of the road vehicle, or between its wheel axles. Known snow-sweeping rollers are subject to a high wear and energy consumption.
By contrast, the invention is based on equipping a snow-sweeping roller with a control device to make possible both low-wear operation and low energy consumption. The snow-sweeping roller of the invention is particularly suited for use in combination with a snow-clearing unit.
According to the invention, low-wear, low-energy snow-sweeping is achieved by using a control device which permits adjustment or modification of roller rotation in accordance with the following control factors;
(a) THe circumferential speed (w) of the roller is adjsuted according to vehicle speed (f); PA1 (b) The circumferential speed (w) of the roller can be set in the range to twice the vehicle speed (f); and PA1 (c) The minimum circumferential speed of the roller (w-min) can be set to a value which will not be reduced even if the vehicle runs slowly or is stationary.
Control factor (a) causes the rotational speed of the roller to increase or decrease with the speed of the utility vehicle. This takes into account the quantity of snow as a function of vehicle speed. This is supplemented by the important condition of control factor (b), according to which the circumferential speed of the roller is equal or larger than the vehicle speed. Circumferential speed can be set to twice vehicle speed--either in discrete or continuously variable steps. For example, with snow levels to 1 cm, a ratio of 1.2 may be sufficient. At higher snow levels, e.g. 4 cm, the ratio of the circumferential roller speed to that of the vehicle may rise to 2.0.
A certain minimum throw width can be achieved, independently of a particular vehicle speed, for example, when the vehicle is stationary or is delayed before a traffic light. Snow is swept laterally from the area next to the vehicle. This is achieved in accordance with control factor (c), by setting a minimum value for the circumferential speed of the roller (w-min). The minimum speed should be set at about 5 km/hour. Even though the achievable throw widths are comparatively short, approximately on the order of 1 to 2 meters, the desired sweeping is accomplished. The roller encounters each patch of snow several times, until it is ejected from the vehicle.
Accordingly, the snow residue which always remains behind a snow plow, for example, can be swept away cleanly from the road surface. In addition to an improved cleaning effect, there also is the additional advantage that less salt must then be used in order to keep the road surface free from icing.
The control equipment is suitably constrained within the framework of the invention. Input data include the rates of roller circumferential speed and vehicle speed, the minimum circumferential speed of the roller, roller diameter, and vehicle speed. The ratio of roller circumferential speed to vehicle speed is essentially a function of snow level. The minimum circumferential speed of the roller (w-min) is generally independent of the sweeping application. In some circumstances, the minimum circumferential speed may depend on the length of the roller. The roller diameter is determined as precisely as possible, taking into account the wear on the bristles. While the input data can be entered by manual setting, vehicle speed is converted into a corresponding input signal, by, for example, a tachometer generator.
The sweeping action tends towards zero when the vehicle speed approaches the maximum circumferential speed of the roller. To warn the driver of the utility vehicle that this situation is being reached, the control equipment generates a warning signal when the maximum circumferential speed of the roller (w-max) has been reached, after going beyond an upper vehicle speed (f-max).
A value of maximum circumferential speed of the roller, obtained from practical driving operation, is about 30 km/hour. This value depends on the maximum power of the roller drive. With hydraulic drive it depends on the maximum rate of flow in the hydraulic system. If the driver hears a warning signal, he reacts by reducing vehicle speed. This assures not only that the circumferential speed of the roller always remains larger than vehicle speed, but also that the ratio of the two speeds is preserved in the established relationship.
In a preferred embodiment of the control device, an electronics system provides an output signal that activates a flow control valve in the pressure control line of a hydraulic roller drive. A regulatable or constant hydraulic pump is used. With a regulatable hydraulic pump, oil flow is adjusted so that a constant pressure difference is always maintained between the pressure side of the hydraulic pump and the load side. With a constant pump, oil flow remains unchanged during load pressure fluctuations. The partial flow that is not used by the load is returned, against load pressure, to the tank.
Power take-off for the hydraulic pump is effected either through an ancillary take-off from the transmission or through an engine powertake-off shaft.